Lennie has just maimed the boss' son. What does Slim do to ensure that George and Lennie won't get fired?

Slim tells Curley that if George and Lennie are fired, he will make sure that everyone will know exactly what happened.... he'll make him a laughing-stock.

Slim smiled wryly. He knelt down beside Curley. "You got your senses in hand enough to listen?" he asked.

Curley nodded. "Well, then listen," Slim went on. "I think you got your han' caught in a machine. If you don't tell nobody what happened, we ain't going to. But you jus' tell an' try to get this guy canned and we'll tell ever'body, an' then will you get the laugh."

"I won't tell," said Curley. He avoided looking at Lennie.